System and method for detecting stuck valves

Abstract

A method of conducting a diagnostic procedure for a braking system includes analyzing via an electronic control unit whether only a first input device is engaged or only a second input device is engaged, conducting a first diagnostic test if only the first input device is engaged, and conducting a second diagnostic test if only the second input device is engaged.

The invention claimed is: 
     
       1. A method of conducting a diagnostic procedure for a braking system, the method comprising:
 analyzing via an electronic control unit whether only a first input device coupled to a first brake circuit is engaged or only a second input device coupled to a second brake circuit is engaged; 
 conducting via the electronic control unit a diagnostic test testing a first valve and a second valve in the first brake circuit, in response to determining that only the first input device is engaged, the diagnostic test including
 during actuation of the first input device, measuring a master cylinder pressure via a first pressure sensor of the first brake circuit and measuring a wheel cylinder pressure via a second pressure sensor of the first brake circuit, 
 comparing a difference between the master cylinder pressure and the wheel cylinder pressure to a threshold pressure value, and determining whether the first valve of the first brake circuit is stuck based on the comparison, 
 upon a release of the first input device, taking second measurements of the master cylinder pressure and the wheel cylinder pressure via the respective first and second pressure sensors of the first brake circuit, 
 comparing the second measurements of the master cylinder pressure and the wheel cylinder pressure and determining whether the second valve of the first brake circuit is stuck based on the comparison; and 
 
 conducting via the electronic control unit a diagnostic test testing a first valve and a second valve in the second brake circuit, in response to determining that only the second input device is engaged, the diagnostic test including
 during actuation of the second input device, measuring a master cylinder pressure via a first pressure sensor of the second brake circuit and measuring a wheel cylinder pressure via a second pressure sensor of the second brake circuit, 
 comparing a difference between the master cylinder pressure and the wheel cylinder pressure to a threshold pressure value, and determining whether the first valve of the second brake circuit is stuck based on the comparison, upon a release of the second input device, taking second measurements of the master cylinder pressure and the wheel cylinder pressure via the respective first and second pressure sensors of the second brake circuit, and 
 comparing the second measurements of the master cylinder pressure and the wheel cylinder pressure and determining whether the second valve of the second brake circuit is stuck based on the comparison. 
 
 
     
     
       2. The method of  claim 1 , further comprising:
 analyzing via the electronic control unit whether both of the first and second input devices are engaged; and 
 conducting, concurrently via the electronic control unit when both of the first and second input devices are engaged, both the diagnostic test testing the first and second valves in the first brake circuit and the diagnostic test testing the first and second valves in the second brake circuit. 
 
     
     
       3. The method of  claim 2 , further comprising:
 analyzing via the electronic control unit whether neither of the first and second input devices is engaged; and 
 conducting via the electronic control unit a diagnostic test in at least one of the first and second brake circuits, wherein fluid pressure to at least one wheel cylinder is generated from within the at least one of the first and second brake circuits, in response to determining that neither of the first and second input devices is engaged. 
 
     
     
       4. The method of  claim 1 , wherein analyzing whether only the first input device is engaged or only the second input device is engaged includes measuring a first pressure at a first master cylinder, and comparing the measured first pressure to a master cylinder threshold pressure value, and measuring a second pressure at a second master cylinder and comparing the second measured pressure to the master cylinder threshold pressure value. 
     
     
       5. The method of  claim 1 , further comprising measuring an engine speed prior to analyzing whether only the first input device is engaged or only the second input device is engaged. 
     
     
       6. The method of  claim 1 , further comprising analyzing a timer with the electronic control unit, to determine a time since a last diagnostic test was conducted prior to analyzing whether only the first input device is engaged or only the second input device is engaged. 
     
     
       7. The method of  claim 1 , further comprising conducting via the electronic control unit a second diagnostic test in response to determining that only the first input device is engaged or in response to determining that both the first brake circuit and the second brake circuit are unactuated, including
 during non-actuation of the second input device, generating a pump pressure directed to a wheel cylinder using a pump and measuring a wheel cylinder pressure via a second pressure sensor of the second brake circuit, 
 comparing the wheel cylinder pressure to the pump pressure and determining whether the first valve of the second brake circuit is stuck based on the comparison, 
 upon release of the pump pressure, taking second measurements of the wheel cylinder pressure via the second pressure sensor of the second brake circuit, and 
 checking the second measurement of the wheel cylinder pressure and determining whether the second valve of the second brake circuit is stuck based on the second measurement of the wheel cylinder pressure. 
 
     
     
       8. The braking system of  claim 7 , wherein the second diagnostic test is performed in response to the electronic control unit determining that both the first brake circuit and the second brake circuit are unactuated. 
     
     
       9. A braking system comprising;
 a first brake circuit including,
 a first master cylinder; 
 a first wheel cylinder positioned at a terminal end of the first brake circuit; 
 a first pressure sensor configured to measure a first master cylinder pressure; 
 a second pressure sensor configured to measure a first wheel cylinder pressure; 
 
 a second brake circuit including,
 a second master cylinder; 
 a second wheel cylinder positioned at a terminal end of the second brake circuit; 
 a first pressure sensor configured to measure a second master cylinder pressure; 
 a second pressure sensor configured to measure a second wheel cylinder pressure; 
 
 a first input device operable to actuate the first master cylinder; 
 a second input device operable to actuate the second master cylinder; and 
 an electronic control unit operable in a first mode in response to determining that only the first input device is actuated and a second mode in response to determining that only the second input device is actuated, 
 wherein, in the first mode, the electronic control unit is programmed to conduct a first diagnostic test of the first brake circuit by comparing values of the first master cylinder pressure and the first wheel cylinder pressure, from the first and second pressure sensors, measured during actuation of the first input device, such that the controller is programmed to diagnose whether a first valve of the first brake circuit is stuck based on the comparison, and by further comparing values of the first master cylinder pressure and the first wheel cylinder pressure, from the first and second pressure sensors, measured upon release of the first input device, such that the controller is programmed to diagnose whether a second valve of the first brake circuit is stuck based on the comparison, 
 and wherein, in the second mode, the electronic control unit is programmed to conduct a first diagnostic test of the second brake circuit by comparing values of the second master cylinder pressure and the second wheel cylinder pressure, from the first and second pressure sensors, measured during actuation of the second input device, such that the controller is programmed to diagnose whether a first valve of the second brake circuit is stuck based on the comparison, and by further comparing values of the second master cylinder pressure and the second wheel cylinder pressure, from the first and second pressure sensors, measured upon release of the second input device, such that the controller is programmed to diagnose whether a second valve of the second brake circuit is stuck based on the comparison, 
 wherein the second mode includes a second diagnostic test of the first brake circuit. 
 
     
     
       10. The braking system of  claim 9 , wherein the electronic control unit is operable in a third mode when the first input device is actuated and the second input device is actuated, wherein the third mode includes the first diagnostic test of the first brake circuit and the first diagnostic test of the second brake circuit. 
     
     
       11. The braking system of  claim 10 , wherein the electronic control unit is operable in a fourth mode when neither the first input device nor the second input device is actuated, wherein the fourth mode includes the second diagnostic test of the first brake circuit and a second diagnostic test of the second brake circuit. 
     
     
       12. The braking system of  claim 11 , further comprising a first pump in the first brake circuit and a second pump in the second brake circuit,
 wherein the electronic control unit is programmed to conduct the second diagnostic test of the first brake circuit in the second mode and the fourth mode by generating a first pump pressure directed to the first wheel cylinder using the first pump and measuring the first wheel cylinder pressure via the second pressure sensor of the first brake circuit, comparing the first wheel cylinder pressure to the first pump pressure, such that the controller is programmed to determine whether the first valve of the first brake circuit is stuck based on the comparison, upon release of the first pump pressure, taking a second measurement of the first wheel cylinder pressure via the second pressure sensor of the first brake circuit, and checking the second measurement of the first wheel cylinder pressure, such that the controller is programmed to determine whether the second valve of the first brake circuit is stuck based on the second measurement of the first wheel cylinder pressure, 
 and wherein the electronic control unit is programmed to conduct the second diagnostic test of the second brake circuit in the first mode and the fourth mode by generating a second pump pressure directed to the second wheel cylinder using the second pump and measuring the second wheel cylinder pressure via the second pressure sensor of the second brake circuit, comparing the second wheel cylinder pressure to the second pump pressure, such that the controller is programmed to determine whether the first valve of the second brake circuit is stuck based on the comparison, upon release of the second pump pressure, taking a second measurement of the second wheel cylinder pressure via the second pressure sensor of the second brake circuit, and checking the second measurement of the second wheel cylinder pressure, such that the controller is programmed to determine whether the second valve of the second brake circuit is stuck based on the second measurement of the second wheel cylinder pressure. 
 
     
     
       13. The braking system of  claim 11 , wherein each of the second diagnostic tests is programmed to the electronic control unit to provide instructions for generating a pump pressure in a corresponding one of the first and second wheel cylinders using a pump in the corresponding one of the first and second brake circuits, measuring a wheel cylinder pressure via the corresponding second pressure sensor, comparing the measured wheel cylinder pressure to the pump pressure, such that the controller is programmed to diagnose whether the first valve of the corresponding one of the first and second brake circuits is stuck based on the comparison, releasing the pump pressure, and checking the wheel cylinder pressure with the second pressure sensor, such that the controller is programmed to diagnose whether the second valve of the corresponding one of the first and second brake circuits is stuck based on the wheel cylinder pressure. 
     
     
       14. The braking system of  claim 9 , further comprising a first pump, wherein, in the second mode, the electronic control unit is programmed to conduct the second diagnostic test of the first brake circuit, the second diagnostic test of the first brake circuit includes generating a first pump pressure directed to the first wheel cylinder using the first pump and measuring the first wheel cylinder pressure via the second pressure sensor of the first brake circuit, comparing the first wheel cylinder pressure to the first pump pressure such that the controller is programmed to determine whether the first valve of the first brake circuit is stuck based on the comparison, upon release of the first pump pressure, taking a second measurement of the first wheel cylinder pressure via the second pressure sensor of the first brake circuit, and checking the second measurement of the first wheel cylinder pressure such that the controller is programmed to determine whether the second valve of the first brake circuit is stuck based on the second measurement of the first wheel cylinder pressure. 
     
     
       15. A method of conducting a diagnostic procedure for a braking system, the method comprising:
 operating an electronic control unit into a first mode in response to identifying via the electronic control unit that a first input device coupled to a first brake circuit is engaged and that a second input device coupled to a second brake circuit is not engaged; 
 in the first mode, the electronic control unit conducting a first diagnostic test testing a first valve and a second valve in the first brake circuit, the first diagnostic test including
 during actuation of the first input device, measuring a master cylinder pressure via a first pressure sensor of the first brake circuit and measuring a wheel cylinder pressure via a second pressure sensor of the first brake circuit, 
 comparing a difference between the master cylinder pressure and the wheel cylinder pressure to a threshold pressure value, and determining whether the first valve of the first brake circuit is stuck based on the comparison, 
 upon a release of the first input device, taking second measurements of the master cylinder pressure and the wheel cylinder pressure via the respective first and second pressure sensors of the first brake circuit, and 
 comparing a difference between the second measurements of the master cylinder pressure and the wheel cylinder pressure to the threshold pressure value, and determining whether the second valve of the first brake circuit is stuck based on the comparison; and 
 
 in the first mode, the electronic control unit conducting a second diagnostic test testing a first valve and a second valve in the second brake circuit, the second diagnostic test including
 during non-actuation of the second input device, generating a pump pressure directed to a wheel cylinder using a pump and measuring a wheel cylinder pressure via a second pressure sensor of the second brake circuit, 
 comparing the wheel cylinder pressure to the pump pressure, and determining whether the first valve of the second brake circuit is stuck based on the comparison, 
 upon release of the pump pressure, taking a second measurement of the wheel cylinder pressure via the second pressure sensor of the second brake circuit, and 
 checking the second measurement of the wheel cylinder pressure, and determining whether the second valve of the second brake circuit is stuck based on the comparison. 
 
 
     
     
       16. The method of  claim 15 , further comprising verifying with the electronic control unit that a vehicle speed is below a threshold value prior to conducting the second diagnostic test.